Perl can now handle every Unicode character property.
A new pod,
perluniprops,
lists all available non-Unihan character properties.
By default the Unihan properties and certain others (deprecated and Unicode internal-only ones) are not exposed.
See below for more details on these; there is also a section in the pod listing them,
and why they are not exposed.

Perl now fully supports the Unicode compound-style of using = and : in writing regular expressions: \p{property=value} and \p{property:value} (both of which mean the same thing).

Perl now fully supports the Unicode loose matching rules for text between the braces in \p{...} constructs.
In addition,
Perl also allows underscores between digits of numbers.

All the Unicode-defined synonyms for properties and property values are now accepted.

qr/\X/,
which matches a Unicode logical character,
has been expanded to work better with various Asian languages.
It now is defined as an extended grapheme cluster.
(See http://www.unicode.org/reports/tr29/).
Anything matched previously that made sense will continue to be matched.
But in addition:

\X will now not break apart a CR LF sequence.

\X will now match a sequence including the ZWJ and ZWNJ characters.

\X will now always match at least one character,
including an initial mark.
Marks generally come after a base character,
but it is possible in Unicode to have them in isolation,
and \X will now handle that case,
for example at the beginning of a line or after a ZWSP.
And this is the part where \X doesn't match the things that it used to that don't make sense.
Formerly,
for example,
you could have the nonsensical case of an accented LF.

\X will now match a (Korean) Hangul syllable sequence,
and the Thai and Lao exception cases.

Otherwise,
this change should be transparent for the non-affected languages.

\p{...} matches using the Canonical_Combining_Class property were completely broken in previous Perls.
This is now fixed.

In previous Perls,
the Unicode Decomposition_Type=Compat property and a Perl extension had the same name,
which led to neither matching all the correct values (with more than 100 mistakes in one,
and several thousand in the other).
The Perl extension has now been renamed to be Decomposition_Type=Noncanonical (short: dt=noncanon).
It has the same meaning as was previously intended,
namely the union of all the non-canonical Decomposition types,
with Unicode Compat being just one of those.

\p{Uppercase} and \p{Lowercase} have been brought into line with the Unicode definitions.
This means they each match a few more characters than previously.

\p{Cntrl} now matches the same characters as \p{Control}.
This means it no longer will match Private Use (gc=co),
Surrogates (gc=cs),
nor Format (gc=cf) code points.
The Format code points represent the biggest possible problem.
All but 36 of them are either officially deprecated or strongly discouraged from being used.
Of those 36,
likely the most widely used are the soft hyphen (U+00AD),
and BOM,
ZWSP,
ZWNJ,
WJ,
and similar,
plus Bi-directional controls.

\p{Alpha} now matches the same characters as \p{Alphabetic}.
The Perl definition included a number of things that aren't really alpha (all marks),
while omitting many that were.
As a direct consequence,
the definitions of \p{Alnum} and \p{Word} which depend on Alpha also change.

\p{Word} also now doesn't match certain characters it wasn't supposed to,
such as fractions.

\p{Print} no longer matches the line control characters: Tab,
LF,
CR,
FF,
VT,
and NEL.
This brings it in line with the documentation.

\p{Decomposition_Type=Canonical} now includes the Hangul syllables.

The Numeric type property has been extended to include the Unihan characters.

There is a new Perl extension,
the 'Present_In',
or simply 'In',
property.
This is an extension of the Unicode Age property,
but \p{In=5.0} matches any code point whose usage has been determined as of Unicode version 5.0.
The \p{Age=5.0} only matches code points added in precisely version 5.0.

A number of properties did not have the correct values for unassigned code points.
This is now fixed.
The affected properties are Bidi_Class,
East_Asian_Width,
Joining_Type,
Decomposition_Type,
Hangul_Syllable_Type,
Numeric_Type,
and Line_Break.

The Default_Ignorable_Code_Point,
ID_Continue,
and ID_Start properties have been updated to their current Unicode definitions.

Certain properties that are supposed to be Unicode internal-only were erroneously exposed by previous Perls.
Use of these in regular expressions will now generate,
if enabled,
a deprecated warning message.
The properties are: Other_Alphabetic,
Other_Default_Ignorable_Code_Point,
Other_Grapheme_Extend,
Other_ID_Continue,
Other_ID_Start,
Other_Lowercase,
Other_Math,
and Other_Uppercase.

An installation can now fairly easily change which Unicode properties Perl understands.
As mentioned above,
certain properties are by default turned off.
These include all the Unihan properties (which should be accessible via the CPAN module Unicode::Unihan) and any deprecated or Unicode internal-only property that Perl has never exposed.

The generated files in the lib/unicore/To directory are now more clearly marked as being stable,
directly usable by applications.
New hash entries in them give the format of the normal entries,
which allows for easier machine parsing.
Perl can generate files in this directory for any property,
though most are suppressed.
An installation can choose to change which get written.
Instructions are in perluniprops.

This pragma turns on Unicode semantics for the case-changing operations (uc/lc/ucfirst/lcfirst) on strings that don't have the internal UTF-8 flag set, but that contain single-byte characters between 128 and 255.

Upgraded from version 0.35_09 to 0.36. Compared to 0.35, this version has a new 'installdeps' action, supports the PERL_MB_OPT environment variable, adds a 'share_dir' property for File::ShareDir support, support the "package NAME VERSION" syntax and has many other enhancements and bug fixes. The 'passthrough' style of Module::Build::Compat has been deprecated.

The Pod specification (perlpodspec) has been updated to bring the specification in line with modern usage already supported by most Pod systems. A parameter string may now follow the format name in a "begin/end" region. Links to URIs with a text description are now allowed. The usage of L<"section"> has been marked as deprecated.

if.pm has been documented in "use" in perlfunc as a means to get conditional loading of modules despite the implicit BEGIN block around use.

Always add a manifest resource to perl.exe to specify the trustInfo settings for Windows Vista and later. Without this setting Windows will treat perl.exe as a legacy application and apply various heuristics like redirecting access to protected file system areas (like the "Program Files" folder) to the users "VirtualStore" instead of generating a proper "permission denied" error.

For VC8 and VC9 this manifest setting is automatically generated by the compiler/linker (together with the binding information for their respective runtime libraries); for all other compilers we need to embed the manifest resource explicitly in the external resource file.

This change also requests the Microsoft Common-Controls version 6.0 (themed controls introduced in Windows XP) via the dependency list in the assembly manifest. For VC8 and VC9 this is specified using the /manifestdependency linker commandline option instead.

Like it has been everywhere else for ages and ages. Also make command-line selection of -UDEBUGGING and -DDEBUGGING work in configure.com; before the only way to turn it off was by saying no in answer to the interactive question.

Ensure that pp_qr returns a new regexp SV each time. Resolves RT #69852.

Instead of returning a(nother) reference to the (pre-compiled) regexp in the optree, use reg_temp_copy() to create a copy of it, and return a reference to that. This resolves issues about Regexp::DESTROY not being called in a timely fashion (the original bug tracked by RT #69852), as well as bugs related to blessing regexps, and of assigning to regexps, as described in correspondence added to the ticket.

It transpires that we also need to undo the SvPVX() sharing when ithreads cloning a Regexp SV, because mother_re is set to NULL, instead of a cloned copy of the mother_re. This change might fix bugs with regexps and threads in certain other situations, but as yet neither tests nor bug reports have indicated any problems, so it might not actually be an edge case that it's possible to reach.

Several compilation errors and segfaults when perl was built with -Dmad were fixed.

If you find what you think is a bug, you might check the articles recently posted to the comp.lang.perl.misc newsgroup and the perl bug database at http://rt.perl.org/perlbug/ . There may also be information at http://www.perl.org/ , the Perl Home Page.

If you believe you have an unreported bug, please run the perlbug program included with your release. Be sure to trim your bug down to a tiny but sufficient test case. Your bug report, along with the output of perl -V, will be sent off to perlbug@perl.org to be analysed by the Perl porting team.

If the bug you are reporting has security implications, which make it inappropriate to send to a publicly archived mailing list, then please send it to perl5-security-report@perl.org. This points to a closed subscription unarchived mailing list, which includes all the core committers, who be able to help assess the impact of issues, figure out a resolution, and help co-ordinate the release of patches to mitigate or fix the problem across all platforms on which Perl is supported. Please only use this address for security issues in the Perl core, not for modules independently distributed on CPAN.